Spray booth

ABSTRACT

A spray booth for use in the electrostatic spraying of powder paint has a spray chamber defined by walls, at least one of which has a wall panel facing inwardly of the spray chamber and made of porous material. An enclosure of gas-impervious material secured in sealed relation to the side of the wall panel opposite to the spray chamber forms, with the panel, a gas chamber, to which gas is supplied under pressure. The gas passes through the porous panel and thereby counteracts deposition of paint powder on the panel, thus facilitating cleaning of the booth and color changeover and reducing color contamination after color changeover.

United States Patent 1191 Vertue Nov. 25, 1975 SPRAY BOOTH [76]Inventor: Charles R. Vertue, 2532A Wharton Primary 8mm Glen Ave.cooksvme, Ontario, Assistant Exammerl)ouglas Salser I Canada Attorney,Agent, or F1rm-Sug.hrue, Rothwell, Mion,

Zinn & Macpeak [22] Filed: Jan. 24, 1974 [21] Appl. No.: 436,236 TRAC Aspray booth for use in the electrostatic spraying of [30] ForeignApplication Priority Data powder pamt has a spray chamber defined bywalls, at D 7 1973 C d 187684 least one of whlch has a wall panel facingmwardly of ec. ana a the Spray Chamber and made of porous material. Anenclosure of gas-impervious material secured in sealed 118/634 fig gif/iz relation to the side of the wall panel opposite to the Spraychamber forms with the panel, a gas Chamber, [58] Field of i g figg towhich gas is supplied under pressure. The gas 1 3 passes through theporous panel and thereby counteracts deposition of paint powder on thepanel, thus fa- [56] References cued cilitating cleaning of the boothand color changeover UNITED STATES PATENTS and reducing colorcontamination after color change- 3,572,287 3/1971 Saito 118/629 over.3,741,155 6/1973 Hunder 118/634 1 3,799,112 3 1974 Huteaux ll8/629 11Claims 4 Drawing Flgures 1 P C P 67 1.7 53 31b, 32b f l.8

31E\ 3Q 51. l 6 14 soak, /-31d "59 51 30c 57 1 19 '23 25 1 t f 2 1 I 122 s p I s1. s5 21. 1 1 2g 58 O (.6

H 15 I f 30G '51. ,2 Lyfib 1.9 5 '1' |--:11z -68 L i US. Patent Nov. 25,1975 Sheet 1 of3 3,921,576

Nov. 25, 1975 Sheet 2 of 3 3 3 @N @N 1 r H 4-: ON 2 m? I a UN? 2? 3m IfV I I l l fl I v I I v {11%, 3 3K. 2m mm U.S. Patent B \fl A H on SPRAYBOOTH The present invention relates to spray booths, and isparticularly, but not exclusively, useful in connection with spraybooths employed for the electrostatic spray ing of powder paints.

In the spraying of powder paints, workpieces suspended on an overheadconveyor are moved by the conveyor in sequence through a spray booth.Within the spray booth, powder paint ejected from a spray gun, andelectrostatically charged on ejection from the gun, is deposited on theworkpieces, which are subsequently conveyed from the spray booth throughan oven where the deposited powder paint is heated to cure the paint.

The spray guns employed to deposit the powder paint on the workpieceswithin the spray booth may be fixed in position or automaticallyreciprocated in the spray booth or may be held in the hand of anoperator standing outside the spray booth and reaching through anopening in one side of the spray booth.

A portion of the spray powder ejected from the spray gun does not becomedeposited on the workpieces, and tends to drift about in the spraychamber and may eventually become deposited on the walls and the bot tomof the spray chamber. Periodically, it is necessary to remove the powderwhich has become deposited on the walls or the bottom of the spraychamber, in order to prevent an excessive build-up of such depositedpowder and also in order to avoid contamination when, having employed apowder paint of one color or polymer, it is desired to change over toutilization of a powder paint of a different color or polymer.

The removal of the powder deposited on the walls and the bottom of thespray chamber necessitates the spray booth being inoperative forconsiderable lengths of time.

It is accordingly an object of the present invention to provide a noveland improved spray booth through which articles to be.sprayed can bemoved on a conveyor and in which deposition of sprayed but unused paintpowder on the walls of the spray booth is counteracted.

According to the present invention, a spray booth comprises a pluralityof walls defining a spray chamber, at least one of said walls comprisinga wall panel having one side facing inwardly of said spray chamber, saidwall panel comprising a porous material, an enclosure of gas-imperviousmaterial at the opposite side of said wall panel and secured in sealedrelationship to said wall panel to form with said panel a gas chamber,and means for supplying gas under pressure into said gas chamber.

In operation, gas, preferably air, supplied under pressure into the gaschamber passes through the porous material of the wall panel into thespray chamber. The effect of the passage of gas from the side of thewall panel facing inwardly of the spray chamber is to carry away fromthe wall panel the majority, if not all, of any sprayed but unusedparticles of paint powder drifting around within the spray chamber. Inthis way, deposition of such sprayed but unused paint powder particleson the wall panel is effectively counteracted.

The spray chamber is defined by a top, a bottom and four vertical wallsforming the front, rear and side walls of the spray chamber, and eachhaving a wall panel comprising a porous material and an enclosure ofgasimpervious material on the opposite side of the wall panel to thespray chamber. An opposed pair of the walls are formed with openingsfrom the passage through the spray booth of a conveyed workpiece.Opposed walls of an outer housing, spaced outwardly of the spray chamberwalls, are also formed with openings for the passage of conveyedworkpieces or one or more openings for workpieces introduced into thespray chamber by hand or on a trolley, and the openings of the opposedwalls of the outer housing are joined by the partitions to the openingsof the spray chamber walls, the partitions forming inlet and outletpassages for the workpieces. The partition walls of the outlet passageare formed with slots, through which gas is discharged under pressure ordrawn by vacuum to form a gas curtain across the outlet passage, whichprevents leakage from the outer housing of sprayed but unused paintparticles.

The invention will be more readily understood from the followingdescription of the preferred embodiment thereof given by way of examplewith reference to the accompanying drawings, in which:

FIG. 1 shows a diagrammatic view, taken in perspective, of a spray boothwith the cover of the spray booth omitted to facilitate illustration ofthe interior of the spray booth;

FIG. 2 shows a plan view of the spray view of FIG. 1 with the cover ofthe spray booth in position;

FIG. 3 shows a plan view taken in horizontal section through the spraybooth of FIGS. 1 and 2; and

FIG. 4 shows a view taken in section through one wall of the spraychamber along the line IVIV of FIG. 3.

Referring firstly to FIGS. 1 to 3 of the accompanying drawings, thespray booth illustrated in those figures has an outer housing which isindicated generally by reference numeral 10 and which is made of sheetmetal.

The outer housing 10 has a front wall in the form of a pivoted door 1 1,a rear wall 12, opposed side walls 13 and 14, a bottom 9 and a coverformed in two separate halves and 71 and an opening (not shown) may beprovided for the egress of powder overspray.

Spaced inwardly of the walls of the housing 10, there is a spray chamberhaving, as shown in FIGS. 1 and 4, a front wall 15, a rear wall 16,opposed side walls 17 and 18, a top 7 and a bottom 8, of which thelatter two are shown partly broken away in FIG. 4.

The side walls 13 and 14 of the outer housing 10 are fonned withopenings in the form of vertical slots 19 and 20.

The side walls 17, 18 of the spray chamber are formed with twocorresponding openings in the form of vertical slot 21, 22. Partitionwalls 23, 24 and 25 extend between the slot 19 in the wall 13 of theouter housing 10 and the slot 21 in the wall 17 of the spray chamber.The partition walls 23, 24 and 25 form an upwardly open outlet passagefor the purpose described hereinafter.

Similarly, the slot 20 in the outer housing wall 14 and the slot 22 inthe spray chamber wall 18 are joined by partition walls 27, 28 and 29,forming an upwardlyopen inlet passage.

The walls 15, 16, 17 and 18, the top 7 and the bottom of the spraychamber are formed by wall panels 30a to 30f extending around the spraychamber. Each of these wall panels has an inner face facing inwardly ofthe spray chamber and, at its opposite side, an outer face which issurrounded by a gas-impervious enclosure 31a to 31f, respectively. Theenclosures 31a to 31f are made of sheet metal and form, together withthe wall panels 30a to 30f, gas chambers 32a to 32f.

The wall panels 30a to 30fare made of a porous material. This porousmaterial may, for example, comprise porous polyvinylchloride, ceramicmaterial or a porous asbestos, which may be in the form of webbing ormatting, and accordingly it is to be understood that the expressionpanel as employed in this disclosure and in the following claims is notintended to be restricted to rigid or self-supporting panels but mayinclude panels of a flexible material such as webbing or matting.

A compressed air pump, illustrated diagrammatically at P, is connectedby pipelines 43 to 53 to the interiors of-the gas chambers 32a to 32fforsupplying air under pressure into the latter.

The partition walls 23 and 24 of the outlet passage are formed withvertical, opposed suction slots 54 and 55. Channel-shaped housing 56 and57 are provided over the slots 54 and 55, respectively, at the outersides of the outlet passage partition walls 23 and 24 for applying apartial vacuum to the suction slots 54 and 55. The vacuum is applied tothe interiors of the channelshaped housings 56 and 57 by pipes 58 and 59extending from a vacuum pump VP, which is connected to a vacuum unit VUfor collecting powder drawn in through the slots 54 and 55.

The spray chamber front wall 15 is secured by vertical hinges, of whichone is illustrated in FIG. 3 and indicated by reference numeral 60, tothe spray chamber wall 17 and is pivotable from the position in which itis shown in FIG. 3 into an opened position to permit access to theinterior of the spray chamber. Alternatively, the spray chamber could beprovided with a horizontally pivotal door (not shown). It will, ofcourse, be appreciated that the door 1 1 forming the front wall of theouter housing must be opened before the spray chamber door formed by thewall can be fully opened. A latch 61 of any suitable type is providedfor securing the outer housing door 11 in its closed position.

Spray nozzles 64 are mounted on the inner sides of the spray chamberwalls 15 and 16 for discharging a spray of powder paint across thecentral portion of the spray chamber from opposite sides thereof. Thespray powder, entrained in a stream of compressed air, is supplied tothe spray nozzle 64 through pipelines 65 to 68, the powder being pickedup in the stream of compressed air from a hopper (not shown) by means ofa powder pickup device illustrated diagrammatically by C.

As can be seen from FIG. 2, the cover of the spray booth is provided astwo separate halves 70 and 71, which are spaced apart by a gap 73. Thegap 73, which extends across the whole of the spray booth and throughthe top 7 of the spray chamber, is disposed directly above and inalignment with the inlet and outlet passages defined by the partitionwalls 23, 24, 27 and 28. The purpose of these inlet and outlet passagesand of the gap 73 is to allow a workpiece 74, shown in FIG. 1, to becarried on an overhead conveyor through the spray chamber, spraying ofopposite sides of the workpiece 74 being effected by the spray guns 64during the passage of the workpiece 74 through the spray chamber.

Suction slots (not shown) corresponding to the suction slots 54 and 55,and associated housings (not shown) corresponding to the housings 56 and57 may 4 be provided horizontally along the gap 73 and vertically alongthe slot 20 to further assist in preventing the egress of excess powder.

In the present embodiment of the invention, the spray booth is intendedfor use with workpieces, such as the workpiece 74, in the form ofvertically extending plates, and accordingly the inlet and outletpassages between the walls of the spray chamber and the outer housing 10are formed as upwardly open vertical slots. However, it will of coursebe appreciated that the invention is in no way restricted to suchworkpiece or passage shapes, and that the shapes and disposition of theinlet and outlet passages for the workpieces may be varied in dependenceon the shape of the workpieces which are to be sprayed and may, forexample, take the form of horizontal slots. Also, the workpiece could berotated as it is sprayed. Moreover, the invention is not restricted toclosed spray booths such as that illustrated in the accompanyingdrawings, but may with advantage also be employed in spray booths of thetype which are formed with an opening in one side through which sprayingis effected by an operator manually supporting a spray gun, or indeed inspray booths in which workpieces are stationary instead of beingsupported by a conveyor.

In operation, workpieces such as the workpiece 74 are fed in successionthrough the inlet and outlet passages and the spray chamber, and thencethrough an oven for heating powder paint sprayed and electrostaticallydeposited on the workpieces in the spray chamber. During such operation,compressed air is supplied to the gas chambers 32a to 32f from the pumpP through the pipelines 43 to 51. The compressed air thus supplied tothe interiors of the gas chambers 32a to 32f passes through the porouswall panels 30a to 30f and counteracts deposition thereon of spraypowder discharged by the spray guns 64 and not deposited on theworkpieces; Such unused sprayed powder may be collected by a hopper (notshown) at the bottom of the spray booth and recirculated to the sprayguns 64.

The sprayed but unused powder within the spray chamber is prevented fromescaping from the spray booth through the outlet passage by being drawnthrough the vacuum slots 54 and 55 in the outlet passage partition walls23 and 24 and collected in the vacuum unit VU.

It has been found in practice that the passage of the compressed airthrough the porous wall panels 30a to 30f materially reduces depositionof the paint powder on these wall panels, and in this way facilitatescleaning of the interior of the spray booth, and is of particularadvantage in enabling rapid changeover from powder paint of one color topowder paint of another color without contamination of the workpieces bypowder paint of the intially or previously employed color. In this way,the time required to change over from the use of one powder paint colorto a different powder paint color can be substantially reduced, so thatundesirably long periods during which the spray booth cannot be employeddue to changeover of powder paint color are avoided.

I claim:

1. A spray booth comprising:

a top, a bottom and a plurality of walls defining a spray chamber;

at least one of said walls comprising a wall panel having one sidefacing inwardly of said spray chamber; said -wall panel comprising aporous material;

an enclosure of gas-impervious material at the opposite side of saidwall panel and secured in sealed relationship to said wall panel to formwith said panel a gas chamber;

means for supplying gas under pressure into said gas chamber;

an outer housing spaced outwardly of said walls;

an opposed pair of said walls and opposed walls of said outer housingdefining upwardly open openings for the passage of a conveyed workpiecethrough said spray booth and through said spray chamber; and

partition walls extending from the openings in said opposed spraychamber walls to said opposed outer housing walls and forming an inletpassage and an outlet passage for movement of the workpiece to and fromthe interior of said spray chamber.

2. A spray booth as claimed in claim 1, wherein said porous materialcomprises porous asbestos.

3. A spray booth as claimed in claim 1, wherein said porous materialcomprises porous polyvinylchloride.

4. A spray booth as claimed in claim 1, wherein said partition walls ofthe outlet passage define suction slots, and means are provided forapplying a partial vacuum to said suction slots to suck unused spraymaterial from said outlet passage.

5. A spray booth comprising:

a top, a bottom and four walls defining a spray chamber, said four wallsforming front, rear and side walls of said spray chamber;

each of said top, said bottom and said four walls comprising a panelhaving one side facing inwardly of said spray chamber;

each of said panels comprising a porous material;

at least one enclosure of gas-impervious material at the opposite sideof each of said panels; said enclo- 6 sures being secured in sealedrelationship to the respective panels to form, with said panels, gaschambers;

means for supplying gas under pressure into said gas chambers;

an outer housing spaced outwardly of said walls;

an opposed pair of said walls and opposed walls of said outer housingdefining upwardly open openings for the passage of a conveyed workpiecethrough said spray booth and through said spray chamber; and

partition walls extending from the openings in said opposed spraychamber walls to said opposed outer housing walls and forming an inletpassage and an outlet passage for movement of the workpiece to and fromthe interior of said spray chamber.

6. A spray booth as claimed in claim 5, wherein said enclosures areformed by sheet metal sealingly secured to said panels, and said porousmaterial comprises a rigid, self-supporting material.

7. A spray booth as claimed in claim 5, wherein an opposed pair of saidwalls define openings for the passage of a conveyed workpiece throughsaid spray chamber, and at least one spray gun is mounted within saidspray chamber.

8. A spray booth as claimed in claim 5, wherein one of said wallscomprise a door pivotable into an open position to allow access to thespray chamber.

9. A spray booth as claimed in claim 5, wherein said walls are spacedinwardly of an outer housing.

10. A spray booth as claimed in claim 5, wherein said porous materialcomprises porous asbestos.

11. A spray booth as claimed in claim 5, wherein said porous materialcomprises porous polyvinylchloride.

l =ll=

1. A spray booth comprising: a top, a bottom and a plurality of wallsdefining a spray chamber; at least one of said walls comprising a wallpanel having one side facing inwardly of said spray chamber; said wallpanel comprising a porous material; an enclosure of gas-imperviousmaterial at the opposite side of said wall panel and secured in sealedrelationship to said wall panel to form with said panel a gas chamber;means for supplying gas under pressure into said gas chamber; an outerhousing spaced outwardly of said walls; an opposed pair of said wallsand opposed walls of said outer housing defining upwardly open openingsfor the passage of a conveyed workpiece through said spray booth andthrough said spray chamber; and partition walls extending from theopenings in said opposed spray chamber walls to said opposed outerhousing walls and forming an inlet passage and an outlet passage formovement of the workpiece to and from the interior of said spraychamber.
 2. A spray booth as claimed in claim 1, wherein said porousmaterial comprises porous asbestos.
 3. A spray booth as claimed in claim1, wherein said porous material comprises porous polyvinylchloride.
 4. Aspray booth as claimed in claim 1, wherein said partition walls of theoutlet passage define suction slots, and means are provided for applyinga partial vacuum to said suction slots to suck unused spray materialfrom said outlet passage.
 5. A spray booth comprising: a top, a bottomand four walls defining a spray chamber, said four walls forming front,rear and side walls of said spray chamber; each of said top, said bottomand said four walls comprising a panel having one side facing inwardlyof said spray chamber; each of said panels comprising a porous material;at least one enclosure of gas-impervious material at the opposite sideof each of said panels; said enclosures being secured in sealedrelationship to the respective panels to form, with said panels, gaschambers; means for supplying gas under pressure into said gas chambers;an outer housing spaced outwardly of said walls; an opposed pair of saidwalls and opposed walls of said outer housing defining upwardly openopenings for the passage of a conveyed workpiece through said spraybooth and through said spray chamber; and partition walls extending fromthe openings in said opposed spray chamber walls to said opposed outerhousing walls and forming an inlet passage and an outlet passage formovement of the workpiece to and from the interior of said spraychamber.
 6. A spray booth as claimed in claim 5, wherein said enclosuresare formed by sheet metal sealingly secured to said panels, and saidporous material comprises a rigid, self-supporting material.
 7. A spraybooth as claimed in claim 5, wherein an opposed pair of said wallsdefine openings for the passage of a conveyed workpiece through saidspray chamber, and at least one spray gun is mounted within said spraychamber.
 8. A spray booth as claimed in claim 5, wherein one of saidwalls comprise a door pivotable into an open position to allow access tothe spray chamber.
 9. A spray booth as claimed in claim 5, wherein saidwalls are spaced inwardly of an outer housing.
 10. A spray booth asclaimed in claim 5, wherein said porous material comprises porousasbestos.
 11. A spray booth as claimed in claim 5, wherein said porousmaterial comprises porous polyvinylchloride.